In article .com,
Steve wrote:
In some contexts, when noise is a problem, people will say that you
want to keep the "noise antenna" that you use with the ANC-4 as small
as possible. This is because you want the noise antenna to hear *only*
the noise, which will be phased out, and not the target signal, which
you don't want to be phased out. The suggestion here is clearly that,
if your noise antenna *does* hear the target signal, you're going lose
signal along with noise.

However, when people use the ANC-4 to establish phased arrays of two or
more antennas, this is usually with a couple of serious antennas,
widely separated, *both* of which can hear the target signal. Hence my
question: When the ANC-4 is connected to two largish antennas, both of
which are capable of hearing the target signal, what prevents the
desired signal from simply being phased out? Is determining what gets
phased out just a matter of carefully adjusting the controls on the
ANC-4?

A noise bridge works by subtracting the noise from the signal. (The
adjustments work by making the time delay, the polarity, and the amplitude
of the noise antenna signal to be the same as the noise coming in on the
main antenna so it can be subtracted). Thus forming an antenna that,
electrically, looks like the difference between the two antennas. So,
to work, you need two antennas that receive the noise and desired signals
in different ratios.

Say, you have a main antenna that picks up signal and noise, and you
have a noise antenna that picks up 10 times as much noise as the
signal. After you adjust your noise bridge to match the amplitude,
the desired signal on the noise channel is only one tenth that on the
main antenna, and that's all you'll lose.

You can get this different noise-to-desired ratio by either putting the
noise antenna as close as possible to the source, or using a directional
antenna. As I remember another poster there, (Ron Hardin?), it often
works better to use a loop to null out the desired signal and just get
the noise and then use the ANC-4 to combine that with another antenna.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)